The prior art patents directed to tubes removable from radiators or heat exchangers are best illustrated by Murray U.S. Pat. No. 3,391,732, Smith U.S. Pat. No. 1,601,226 and British Pat. No. 502,604. The present invention presents a new and novel sealing construction for installing and holding removable heat exchanger tube assemblies in heavy duty radiators permitting ready removal of each individual tube should it become defective without having to remove the headers or other parts of heavy duty radiators or other heat exchangers.